I log about 20 IP's a day testing my site for vulnerabilities to SQL injections, javascript injections, directory traversal, XSS and more. Theres no way these are humans. Although these things are a pain in the ass because I have to sift through pages of this crap when I'm looking for human activity, I like the idea of programming bots to scour the internet and do stuff for you. How do these bots work, do they use search engines or something? Is there a great deal of programming knowledge required to be able to build a simple bot?

There are plenty of kinds of bots. The kind you are talking about will connect to your site the same way a person would, and just inject code to test if your site is vulnerable.

It's not particularly hard to code a bot. You have to (generally) do the following

1: Connect to a server2: Request or Receive data from the server.3: Automate reading through it (Probably by manipulating strings and using if-then statements)4: Based on #3, have the bot send some sort of reply, or do whatever you want it to do.

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